deps(deps): bump kotlin.version from 2.2.20 to 2.3.21 (#29)

Bumps `kotlin.version` from 2.2.20 to 2.3.21.

Updates `org.jetbrains.kotlin:kotlin-stdlib-jdk8` from 2.2.20 to 2.3.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.2.20...v2.3.21)

Updates `org.jetbrains.kotlin:kotlin-test` from 2.2.20 to 2.3.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.2.20...v2.3.21)

Updates `org.jetbrains.kotlin:kotlin-maven-plugin` from 2.2.20 to 2.3.21

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-stdlib-jdk8
  dependency-version: 2.3.21
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.jetbrains.kotlin:kotlin-test
  dependency-version: 2.3.21
  dependency-type: direct:development
  update-type: version-update:semver-minor
- dependency-name: org.jetbrains.kotlin:kotlin-maven-plugin
  dependency-version: 2.3.21
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

pom.xml

@@ -48,7 +48,7 @@
         <!-- Runtime / library dependencies -->
         <flexmark.version>0.64.8</flexmark.version>
         <jackson.bom.version>2.21.3</jackson.bom.version>
-        <kotlin.version>2.2.20</kotlin.version>
+        <kotlin.version>2.3.21</kotlin.version>
         <logback.version>1.5.32</logback.version>
         <lombok.version>1.18.46</lombok.version>
         <pdfbox.version>3.0.7</pdfbox.version>